In a 1995 article in the American Journal of Public Health, Philip Lee and Felicia Stewart from the US Department of Health and Human Services stated that more than half of all pregnancies in the US are unintended and failing to prevent them is not only medically costly, but also personally and socially costly as well. The use of available contraceptive methods, whether natural or artificial, can thus be extremely cost effective as compared with using no contraception.
However, a number of problems a reassociated with available contraceptive methods. Artificial contraceptive methods, such as oral contraceptives, have health risks associated with long term use and are not approved for use by some religious groups. In the case of barrier methods, there are also problems for those who are allergic to latex rubber.
Natural family planning, on the other hand, is recommended by some religious groups. With proper training and commitment, it can be an effective contraceptive method. Moreover, it is non-invasive and involves no chemicals. A number of natural methods have been used to monitor ovulation, including basal temperature tracking, calendar tracking, and luteinizing hormone urine test.
However, these natural methods of family planning are beset with a number of disadvantages. In the case of basal temperature, measurement needs to be performed early in the morning and demands continual monitoring, which renders the test very in convenient.
Moreover, while it is considered the most reliable simple test, it does not provide a forewarning of ovulation. Calendar tracking is also tedious, time consuming, and provides no indicator of actual ovulation. Luteinizing hormone urine test is messy, difficult to administer, inconvenient, and can be expensive.
Currently available natural methods of family planning are made more difficult by the variability of one female's fertility cycle to another. In addition, an individual female's own fertility cycle is subject to erratic changes due to various internal and external factors, such as psychological stress, drugs, ovarian cyst, and sexually transmitted diseases. The currently available tests for fertility have not substantially improved reliability because those tests are qualitative and are thus themselves subject to the same variability that affect fertility cycle. As it has been widely accepted that a woman can conceive from an act of intercourse for a maximum of only about seven days of her menstrual cycle, the reliability of natural family planning thus depends on identifying this fertility time window without ambiguity.
One of the tests that have been used to monitor fertility cycle is the ferning test. Ferning, a widely studied phenomenon, is a physical state assumed by dried saliva during the period of ovulation. The physical basis of ferning is not known, but it does roughly correlate with increases in the chloride content of the saliva. Thus, changes in ionic strength and/or the content of sodium or potassium in the saliva appear to be factors; possible changes in the molecular species of mucopolysaccharides cannot be ruled out. Feming can be viewed with a low magnification lens, but this method is not quantitative, since some degree of ferning can be observed four to six days prior to ovulation. Consequently, this method of detection can be misleading as a gauge for ovulation.
U.S. Pat. No. 4,815,835 to Corona and U.S. Pat. No. 5,572,370 to Cho disclose a qualitative, optical-based ferning tests comprising a light source and lenses to determine female fertility status using the subject's saliva. In an article in Advances in Contraception (volume 9, 1993, pages 335-340) Barbato et al. disclose another qualitative ferning test using a pocket microscope and a slide for the saliva samples. All of these tests are based solely on qualitative evaluation of the extent of ferning formation in saliva samples, and are thus subject to inaccuracies and uncertainties due to erratic variations in symptoms associated with female fertility. It is therefore desirable to quantitatively monitor female fertility cycle on the basis of ferning. And it is also desirable to quantitatively determine the degree of ferning in a female and correlate such ferning degree to the ovulation status of the female.